Modular extrusion die

ABSTRACT

Extrusion tool or die for the extrusion of metallic material, in particular a material of aluminium or alloys thereof, or other non-ferrous metals such as Cu and alloys thereof. The die is a modular type comprising die plate/s ( 2, 3 ) with cavitie/s ( 4, 5 ) provided with insert/s ( 6, 7 ). The area of the die with strong thermo-mechanical solicitation comprising the die plate/s ( 2, 3 ), is made of a nickel, iron or cobalt-based super alloy, whereas the die in the area with strong tribological solicitation comprising the insert/s, i.e. the mandrel ( 6 ) and/or the bearing ( 7 ) of the die, is manufactured of a wear resistant material which may be a high speed tool steel, a precipitation hardened steel or a high alloy hot-worked steel, or any of suitable steel types provided with a coating such as nano particle or CVD.

The present invention relates to an extrusion tool or die for theextrusion of metallic material, in particular a material of aluminium oralloys thereof, or other non-ferrous metals such as Cu and alloysthereof.

Extrusion is a process used to create solid or hollow objects of a fixedcross sectional profile. The material is pushed through the die of thedesired cross section. The two main advantages of the extrusion processover other manufacturing processes is its ability to create very complexcross-sections and finished parts with an excellent surface finish.

The dies are, depending of course on the material being extruded andtemperature etc., subjected to wear and numerous attempts have been madeto improve the life time of extrusion dies for example by selectingsuitable die materials, heat treatment and/or coating of the die withdifferent types of coating such as CVD or nano particle type coatings.

From U.S. Pat. No. 0,416,9366 is known an extrusion device for theextrusion of hollow or semi-hollow sections of metal, in particularaluminium. The device has at least one mandrel support projecting intothe die opening where the mandrel head is a special insert type which isheld in place on a mandrel support by a connecting device.

U.S. Pat. No. 0,477,3251 is related to a 2 part die, whereof one partincludes the bearing and the other being the support. The specificity ofthis solution appears to be that the two die parts are atomically bondedusing powder metallurgy technology. Further, the “support” part (the onethat does not carry the bearing) is relatively vaguely defined in termsof material selection as a “tough non-ductile heat resistant steel of acomposition different from the metallic material of the bearing holdingpart”.

JP-06315716 further relates to an extrusion die with a tool comprising amaterial made of a Ni base alloy and having hardness after heattreatment of more than HRC 33. The purpose of using such alloy is toprevent the penetration of Zn into the tool, i.e. preventing Zincembrittlement.

Still further CN-201287153 shows an aluminium profile extrusion diewhere the die tools, i.e. the parts forming the extrusion profileopening are replaceable and are made from a wear resistant material.

With the present invention is provided an extrusion die where thelifetime is quite considerably extended and where the cost ofreplacement and maintenance accordingly is reduced. Tests performed inseveral aluminium extrusion plants of the applicant shows that theselection of Ni-base super alloys as die material according to theinvention reduces sever cracking and improves the die lifetime fromone/two hundred extruded billets to thousand and more extruded billetsbefore replacement of die parts or maintenance is needed.

The invention is characterized by the features as defined in theenclosed independent claim 1.

Advantageous embodiments of the invention are further defined in thedependent claims 2-7

The invention will be further described in the following by way ofexample and with reference to the drawings, where:

FIG. 1 shows an example of an extrusion die according to the invention,a) assembled in cross section, b) the same in expanded view,

FIG. 2 shows in larger scale a cross section part of one of the diecavities shown in FIG. 1 a).

FIG. 3 Shows a Manson-Coffin diagram depicting the linear relationship,on a log-log plot, of plastic strain range versus cycles to failure ofthe most common tool steels, employed for extrusion dies, with thefatigue properties of a superalloy according to the invention.

As stated above, extrusion is a process used to create solid or hollowobjects of a fixed cross sectional profile. The attached figures show anexample of an extrusion tool or die 1 for extruding hollow profileswhich will be further explained in the following. The extrusion die 1 asshown in FIG. 1 a) and b) includes one bridge die body 2 and one platedie body 3, each provided with two cavities 4, respectively 5 and eachcavity further defining openings with inserts 6, 7. The die as shown inFIG. 1 represents what is defined as being a two cavity die capable ofextruding two profiles in parallel at the same time. Extrusion dies mayhowever be of one or three or more cavity type depending on the type,shape (design) and size of the die opening forming the extruded productas well as the capacity of the extrusion equipment (ram and block—notshown in the figures).

FIG. 2 shows in larger scale and in cross section one of the diecavities 4, 5 shown in FIG. 1 a). The two die bodies 2, 3 are, in anassembled condition whereby a mandrel part 10 on the bridge die body 2partly protrudes into the opening of the cavity 5 in the die plate 3such that an opening 11 is formed between the mandrel and cavity opening5 in the die 3. The material being extruded is pressed through thisopening 11 thereby forming the shape of the final, extruded hollowproduct.

With the present invention the mandrel 10 is made of a separate mandrelinsert 6 attached to the bridge die body 2 by means of a screw 8.

On the other hand, according to the invention, the opening in the dieplate 3 is made of a separate bearing insert 7, as well being attachedto the die plate 3 by means of second screws 9. In stead of beingconnected by means of screws 9, the bearing insert 7 may as analternative be thermally shrunk fit into a recess in the die plate 3opening 5.

The fundamental idea of the present invention is the selection ofdifferent materials and the combined utilization of these in theappropriate zones of the extrusion die, fitting with thethermo-mechanical solicitations on one side and the tribologicalsolicitations on the other side.

In the area of strong thermo-mechanical solicitation (Creep—Low CycleFatigue regime), the first “modulus” of the die which includes thebridge body 2 and/or die plate body 3 depending as stated above onwhether it is a hollow or solid profile, is made of a Superalloy. Inparticular the Superalloys are based either on a) Nickel, b) Cobalt orc) Iron. The Nickel, Cobalt and Iron based Superalloys ranges mayrespectively be defined as follows:

Nickel based superalloys: Ni (min 39% max 78%), Fe (min 0% max 36%), Cr(min 12% max 25%), Al (min 0% max 5%), Co (min 0% max 20%), Mo (min 0%max 10%), Nb (min 0% max 5%)Cobalt based superalloys: Co (min 34% max 50%), Ni (min 10% max 29%), Fe(min 3% max 26%), Cr (min 3% max 22%), Al (min 0% max 6%), Nb (min 0%max 3%), W (min (0% max 15%)Iron based superalloys: Fe (min 42% max 74%), Ni (min 0% max 38%), Cr(min 0% max 20%), Al (min 0% max 5%), Co (min 0% max 15%), Mo (min 0%max 5%), Nb (min 0% max 5%)

Above defined Superalloys, or high-performance alloy, are alloys thatexhibit excellent mechanical strength and creep resistance at hightemperatures, good surface stability, and corrosion and oxidationresistance.

Superalloys develop high temperature strength through solid solution orprecipitation strengthening: to a first approximation the elevatedtemperature strength of a superalloy depends upon the amount anddistribution of the strengthening intergranular second phase, which isγ′ in the case of Nickel-based Superalloys and carbides in the case ofcobalt-base Superalloys.

Superalloys retains strength over a wide temperature range, attractivefor high temperature applications where steels would succumb to creep asa result of thermally-induced crystal vacancies.

Creep resistance is dependent on reducing the speed of dislocationswithin the crystal structure. The body centred cubic gamma prime phase[Ni₃(Al,Ti)], present in nickel and nickel-iron Superalloys, presents abarrier to dislocations. Chemical additions such as Aluminium andTitanium promote the creation of the gamma prime phase (γ′). The gammaprime phase size can be finally controlled by annealing. Many otherelements, can be present; Chromium, Molybdenum, Tungsten, Aluminium,Zirconium, Niobium, Rhenium, Ccarbon or Silicon are a few examples.

Regarding at the Cobalt base Superalloys, considerable amount ofrefractory elements are employed in solution strengthened structure,such as chromium, molybdenum or tungsten. These solutes have inhibitingrecovery capacity and they obstruct the dislocations movement. Carbides,precipitated at grain boundaries, block the grain boundaries sliding andproduce along high rupture life.

Other crucial material properties are fatigue life, phase stability, aswell as oxidation and corrosion resistance.

Generally, solid-solution-strengthened alloys are expected to havestrong resistance to fatigue cracking due to an increased resistance toslip and an enhanced strain hardening capacity.

In general, high temperature fatigue may be thought of a cyclic creeprupture process. For this reason, the relationships betweenmicrostructure, creep deformation and fracture, previously described,are applicable.

Focusing on the corrosion and oxidation resistance, the strongresistance against environmental effects is provided by the formation ofa protective oxide layer which is formed, by elements such as aluminiumand chromium, when the metal is exposed to oxygen and encapsulates thematerial, and thus protecting the rest of the component.

Namely, but non-exhausitvely, the alloys hereafter identified in table 1by their UNS, ISO or AFNOR norms are examples falling into the abovedescribed families. The table contains, for indicative purpose one ofthe well-established trade-name of the alloys.

TABLE 1 primary list of High temperature performance Superalloys coveredby the present invention. Well-established commercial name Norm(UNS-ISO-AFNOR) INCONEL®  alloy 600 UNS N06600 INCONEL®  alloy 601 UNSN06601 INCONEL®  alloy 617 UNS NO6617 INCONEL®  alloy 625 UNS N00625INCONEL®  alloy 625LCF® UNS N06626 INCONEL®  alloy 706 UNS N09706INCONEL®  alloy 718 UNS N07718 INCONEL®  alloy 718SPF™ UNS N07719INCONEL®  alloy X-750 UNS N07750 INCONEL®  alloy MA754 UNS N07754INCONEL®  alloy 783 UNS R30783 INCONEL®  alloy HX UNS N06002 NIMONIC® alloy 75 UNS N06075 NIMONIC®  alloy 80A UNS N07080 NIMONIC®  alloy 90UNS N07090 NIMONIC®  alloy 105 ISO NW 3021 NIMONIC ® alloy 115 AFNOR NCK15 ATD NIMONIC®  alloy 263 UNS N0726 NIMONIC®  alloy 901 UNS N09901NIMONIC®  alloy PE11 AFNOR Z 8 NCD 38 NIMONIC®  alloy PE16 AFNOR NW 11AC NIMONIC®  alloy PK33 AFNOR NC 19 KDU Waspaloy UNS N07001 INCOLOY® alloy 903 UNS N19903 INCOLOY®  alloy 909 UNS N19909 INCOLOY®  alloyMA956 UNS S67956 INCOLOY®  alloy A-286 UNS S66286 UDIMET®  alloy 188 UNSR30188 UDIMET®  alloy 500 UNS N07500 UDIMET®  alloy L-605 UNS R30605UDIMET®  alloy 700 SAE AMS 5846 UDIMET®  alloy D-979 UNS N09979 UDIMET® alloy R41 UNS N07041 UDIMAR®  alloy 250 UNS K92890/UNS K92940 UDIMAR® alloy 300 UNS K93120 MP35N UNS R30035

Additionally to the previous, the following alloys listed in table 2 andidentified by their commercial names and detailed chemical compositionsare also among the explicitly covered materials used for the first“modulus”, i.e. the high thermo-mechanical solicitation area of the die.The materials listed in table 2 are part of the Ni-base Superalloysdefined above:

TABLE 2 Ni-base Superalloys of detailed chemical composition andidentified by their well-established trade-name. Denomination Ni Fe CrAl Co Mo Nb Ti W Y203 Ce Si

NIMONIC ® 65 0 25 0 0 10 0 0 0 0 0.03

alloy 86 NIMONIC ® 48 0 24.2 1.4 19.7 1.5 1 3 0 0 0

alloy 101 UDIMET ® 56 0 19 2 12 6 0 3 1 0 0

alloy 520 UDIMET ® 56 0 16 2.5 14.7 3 0 5 1.25 0 0

alloy 720

indicates data missing or illegible when filed

Additionally to the previous, the following alloy identified by itstrade-name and chemical composition is also among the explicitly coveredmaterials used for the first “modulus”, i.e. the high thermo-mechanicalsolicitation area of the die. The material presented in table 3 is partof the Ni-base Superalloys defined above:

TABLE 3 Chemical composition of Ni-base Superalloy AEREX350 Denomi-nation Ni Fe Cr Al Co Mo Nb Ti W Y203 Ce Si

AEREX 44.5 0 17 1 25 3 1.1 2.2 2 0 0

350

indicates data missing or illegible when filed

On the other hand, in the area of strong tribological solicitation, i.e.friction and wear due to passing alloy being formed, the second modulusof the die which is/are the insert/s, i.e. the so-called bearings ofinserts 6 and 7 (area of the die where the extruded profile takes itsfinal shape) is manufactured of a wear resistant material. Such materialcould be any known wear resistant die material such as a high speed toolsteel, a precipitation hardened steel or a high alloy hot-worked steeand alloys being obtained by a standard forging process, a spray formingtechnique or by powder metallurgy technology or any of such steel ormaterial types provided with surface hardening through nitriding orsimilar process or by a surface coating technology such as chemicalvapour deposition (CVD), Plasma assisted/Enhanced chemical vapourdeposition (PACVD/PECVD), Physical vapour deposition (PVD) or otherspraying processes (Flame Spray, Cold spray/high velocity, Plasma spray,high velocity oxyfuel Spray, etc.)

The selection of a material different from a nickel, iron or cobalt-baseSuperalloy belonging the above described groups for the die inserts is afundamental requirement of the concept of the present invention. Thisparticular combination is crucial for the overall performance of theconcept since 1) the Superalloy in the die body parts 2 and 3 hassuperior high temperature mechanical properties but low tribologicalwear properties while 2) the wear resistant materials in the insertbearing areas 6 and 7 have superior tribological wear properties but lowhigh temperature mechanical properties. Consequently, with the presentinvention is achieved the best possible fit between local materialselection and local mechanical and tribological solicitations. Where thestress is high enough to cause plastic deformation, it's preferable tocharacterise Low-cycle fatigue by the Coffin-Manson relation

$\frac{{\Delta\varepsilon}_{p}}{2} = {\varepsilon_{f}^{\prime}\left( {2N} \right)}^{c}$

where:

-   -   Δε_(p)/2 is the plastic strain amplitude at half life;    -   ε_(f)′ is an empirical constant known as the fatigue ductility        coefficient, the failure strain for a single reversal;    -   2N is the number of reversals to failure (N cycles);    -   c is an empirical constant known as the fatigue ductility        exponent.

A FEA (Finite Element Analyse) simulations, realized on the area of thedie which is thermo-mechanical stressed, demonstrated that thetransition bridge to mandrel have stress concentration beyond yieldlimit (these zones are called “hot spots”): this indicates plasticdeformation of the material which also has been verified throughinelastic simulations. The cyclic behaviour and the registered lifetimesof the extrusion tools show that plastic tensile and compression strainsare present during the extrusion process. For this reason, relative tothe presence of a plastic strain, it is proper to adopt theManson-Coffin relation to discuss the fatigue properties of the diematerial and to benchmark different die solutions.

FIG. 3 shows a linear relationship, on a log-log plot, of plastic strainrange versus cycles to failure. The diagram permits to benchmark thefatigue behaviour of the most common tool steels, employed for extrusiondies, with the fatigue properties of a superalloy. It is clear that thesuperalloy, on equal terms of plastic strain applied at elevatedtemperature, shows a higher fatigue life than a tool steel. The resultshighlight the superior fatigue resistance of the superalloys and confirmthe good adaptability of these materials for the realisation of the areaof the die with a strong thermo-mechanical solicitation

The present invention as defined in the claims is not restricted to theabove two cavity die example for extruding hollow profiles based dieinserts 6 and 7, but may be one or a three or more cavity type and alsosingle or more cavity die plate for extruding solid profiles.

The invention as defined in the claims is further not restricted to thedesign as regards the interconnection of the die parts and inserts bymeans of screws as shown in the figure and described above, but may besecured to one another or interconnected by shrink fit or otherconnecting means.

1-7. (canceled)
 8. Extrusion tool or die for the extrusion of metallicmaterial, in particular a material of aluminium or alloys thereof, orother non-ferrous metals such as Cu and alloys thereof, the die being amodular type comprising die bodie/s with cavitie/s provided withinsert/s, wherein the area of the die with strong thermo-mechanicalsolicitation comprising the die bodie/s, is made of a nickel, iron orcobalt based super alloy, whereas the die in the area with strongtribological solicitation comprising the insert/s, i.e. the mandreland/or the bearing, is manufactured of a wear resistant material. 9.Extrusion die according to claim 8, wherein the die is a two or morecavity die.
 10. Extrusion die according to claim 8, wherein the alloy isa nickel based superalloy containing Ni 39-78 wt %, Fe 0,0-36 wt %, Cr12%-25 wt %, A10,0%-5 wt %, Co (min 0% max 20%), Mo-10 wt %, Nb-5 wt %.11. Extrusion die according to claim 8, wherein the alloy is a cobaltbased superalloy: containing Co 34-50 wt %, Ni 10-29 wt %, Fe 3-26 wt %,Cr 3-22 wt %, A 10,0-6 wt %), Nb 0,0-3 wt %, W 0,0-15 wt %. 12.Extrusion die according to claim 8, wherein the alloy is an iron basedsuperalloys containing Fe 42-74 wt %, Ni 0,0-38 wt %, Cr 0,0-20 wt %,A10,0%-5 wt %, Co-15 wt %, Mo 0,0%-5%, Nb 0,0-5 wt %)
 13. Extrusion dieaccording to claim 8, wherein the wear resistant material is a highspeed tool steel, a precipitation hardened steel or a high alloyhot-worked steel and alloys being obtained by a standard forgingprocess, a spray forming technique or by powder metallurgy technology.14. Extrusion die according to claim 8, wherein the wear resistantmaterial is surface hardened by surface nitriding or similar process oris provided with a surface coating based on chemical vapour deposition(CVD), plasma assisted/enhanced chemical vapour deposition(PACVD/PECVD), physical vapour deposition (PVD) or other sprayingprocesses such as flame spray, cold spray/high velocity, plasma spray orhigh velocity oxyfuel spray.